DESCRIPTION: (Applicant's Description) The Light Source and Confocal Microscopy Facility has two components with the unifying element of service to the investigators in the use of the various lasers and light sources. Services of the Light Source Facility (LSF) are maintenance, characterization and calibration of the light irradiation sources, operation of the lasers, record keeping, training, and consultation. With the use of laser scanning confocal microscopy in the program, the facility has been expanded to include the Confocal Microscopy Facility (CMF). The principal components of the LSF are: (1) The staff, consisting of the Director, Claudio H. Sibata, Ph.D., and the photophysics technician, Mr. John Mulvihill, M.S.; (2) Facilities, including lasers and other light sources, maintenance and repair equipment, work space and tools, and light source records; and (3) LSF equipment for measuring and calibrating light sources. To provide the same service for Project 3, Dr. Chris Lawson, Professor of Physics and Director of the UAB Laser Center, will service and characterize sources at UAB and will report on activities to Dr. Sibata. The principal components of the CMF are: (1) The staff, consisting of the co-Director, Anna-Liisa Nieminen, Ph.D., and the research assistant; and (2) Facilities, which consist of a laser-scanning confocal microscope and accessories. Dr. Sibata is Director of Core A with overall responsibility for the core and for services related to light sources for PDT. Dr. Nieminen is co-director with responsibility for the provision of expertise and training in the use of the confocal microscope under her control. Dr. Sibata will assist Dr. Nieminen in dosimetric assessments when one of the lasers is used to deliver a therapeutic dose in the microscope, or when it is necessary to ascertain the extent of potential damage to cells from the laser.